Erratic viewport FPS at high frame rate #111579

New Issue

Campbell Barton · 2023-08-27T07:00:00+02:00

Campbell Barton commented

2023-08-27 07:00:00 +02:00

When setting the frame to a high value 120+, the FPS value in the viewport becomes erratic and changes a lot, showing a higher values then the desired.

Steps to reproduce:

Disable VSync (in the case of Linux/X11 set the environment variable vblank_mode=0 for AMD, __GL_SYNC_TO_VBLANK=0 for NVidia).
Run blender with factory settings.
Set the FPS to 240.
Play the animation.
Notice the FPS value flickers, changing between 200..400.
Set the FPS to 120.
Notice the FPS value flickers, between 130..140.

This error can be obscured at lower frame-rates but was hidden by the FPS display rounding to integer.

When the FPS display is changed to always show decimal places, an empty scene set to use 23.98 FPS playback results in an actual FPS of 24.03.

Observed in 3.6.1 and current main, both Wayland & X11.
Observed in 2.62 on X11.
Works as expected for 2.49 on X11.

Notes:

As this is quite simple to redo, I'm surprised this hasn't been reported before (from searching online and on this site I couldn't find a report at least).
This works properly in 2.4x and looks to be a regression from 2.5x event system refactor.

Reporting for reference, investigating a fix.

A follow up on this change, at the time I thought this was more of a technical flaw - mainly noticeable when the displayed FPS text jiitered, however comparing the playback speed on an object rotating at a fixed speed, I can notice occasional glitch at 50-FPS on my system.

Attached comparisons for the FPS during playback on a simple file before/after the fix.

Note that the "after" case still has some jittering, !111603 is a proposed fix for that.

25 FPS.

30 FPS.

50 FPS.

60 FPS.

120 FPS.

When setting the frame to a high value 120+, the FPS value in the viewport becomes erratic and changes a lot, showing a higher values then the desired. Steps to reproduce: - Disable VSync (in the case of Linux/X11 set the environment variable `vblank_mode=0` for AMD, `__GL_SYNC_TO_VBLANK=0` for NVidia). - Run blender with factory settings. - Set the FPS to 240. - Play the animation. - Notice the FPS value flickers, changing between 200..400. - Set the FPS to 120. - Notice the FPS value flickers, between 130..140. This error can be obscured at lower frame-rates but was hidden by the FPS display rounding to integer. When the FPS display is changed to always show decimal places, an empty scene set to use 23.98 FPS playback results in an actual FPS of 24.03. - Observed in 3.6.1 and current `main`, both Wayland & X11. - Observed in 2.62 on X11. - Works as expected for 2.49 on X11. Notes: - As this is quite simple to redo, I'm surprised this hasn't been reported before (from searching online and on this site I couldn't find a report at least). - This works properly in 2.4x and looks to be a regression from 2.5x event system refactor. ---- Reporting for reference, investigating a fix. ---- A follow up on this change, at the time I thought this was more of a technical flaw - mainly noticeable when the displayed FPS text jiitered, however comparing the playback speed on an object rotating at a fixed speed, I can notice occasional glitch at 50-FPS on my system. Attached comparisons for the FPS during playback on a simple file before/after the fix. Note that the "after" case still has some jittering, !111603 is a proposed fix for that. 25 FPS. ![](https://projects.blender.org/attachments/133b0a7a-000b-4d87-9699-f8a782a24b1d) 30 FPS. ![](https://projects.blender.org/attachments/da7acf0a-46f1-40ab-b51a-f0a0de6f0e74) 50 FPS. ![](https://projects.blender.org/attachments/9fdb48df-e182-479c-97d1-a59446cbd3ea) 60 FPS. ![](https://projects.blender.org/attachments/d55e2a06-958a-41bb-9c38-46be017cc779) 120 FPS. ![](https://projects.blender.org/attachments/8800f4bd-c119-46b5-bfe2-64cac4ba55c0)

fps_cmp_120.png

122 KiB

fps_cmp_30.png

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fps_cmp_50.png

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fps_cmp_60.png

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fps_cmp_25.png

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Campbell Barton added the

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